<template>
	<div class="yzm">
		<canvas id="canvas2" width="120" height="40"></canvas>
		<span id="changeImg2">看不清换一张</span>
	</div>
</template>

<script>
	export default {
		data() {
			return {
				yzm: ""
			}
		},

		mounted() {
			var _this = this;
			let yzm = "";
			/**生成一个随机数**/
			function randomNum(min, max) {
				return Math.floor(Math.random() * (max - min) + min);
			}
			/**生成一个随机色**/
			function randomColor(min, max) {
				var r = randomNum(min, max);
				var g = randomNum(min, max);
				var b = randomNum(min, max);
				return "rgb(" + r + "," + g + "," + b + ")";
			}
			drawPic();
			document.getElementById("changeImg2").onclick = function(e) {
				yzm="";
				e.preventDefault();
				drawPic();
				_this.$emit("yzm",_this.yzm);
				console.log(_this.yzm);
			}

			/**绘制验证码图片**/
			function drawPic() {
				var canvas = document.getElementById("canvas2");
				var width = canvas.width;
				var height = canvas.height;
				var ctx = canvas.getContext('2d');
				ctx.textBaseline = 'bottom';

				/**绘制背景色**/
				ctx.fillStyle = randomColor(180, 240); //颜色若太深可能导致看不清
				ctx.fillRect(0, 0, width, height);
				/**绘制文字**/
				var str = 'ABCEFGHJKLMNPQRSTWXY123456789';
				for(var i = 0; i < 4; i++) {
					var txt = str[randomNum(0, str.length)];
					yzm += txt;
					ctx.fillStyle = randomColor(50, 160); //随机生成字体颜色
					ctx.font = randomNum(15, 40) + 'px SimHei'; //随机生成字体大小
					var x = 10 + i * 25;
					var y = randomNum(25, 45);
					var deg = randomNum(-45, 45);
					//修改坐标原点和旋转角度
					ctx.translate(x, y);
					ctx.rotate(deg * Math.PI / 180);
					ctx.fillText(txt, 0, 0);
					//恢复坐标原点和旋转角度
					ctx.rotate(-deg * Math.PI / 180);
					ctx.translate(-x, -y);
				}
				/**绘制干扰线**/
				for(var i = 0; i < 8; i++) {
					ctx.strokeStyle = randomColor(40, 180);
					ctx.beginPath();
					ctx.moveTo(randomNum(0, width), randomNum(0, height));
					ctx.lineTo(randomNum(0, width), randomNum(0, height));
					ctx.stroke();
				}
				/**绘制干扰点**/
				for(var i = 0; i < 100; i++) {
					ctx.fillStyle = randomColor(0, 255);
					ctx.beginPath();
					ctx.arc(randomNum(0, width), randomNum(0, height), 1, 0, 2 * Math.PI);
					ctx.fill();
				}
				_this.yzm = yzm;
			}
			_this.$emit("yzm",_this.yzm);
		}
	}
</script>

<style>
	.yzm {
		display: inline-block;
		vertical-align: middle;
	}
	
	.yzm>canvas {
		margin-left: 8px;
	}
	
	.yzm>span {
		vertical-align: 15px;
		cursor: pointer;
		margin-left: 8px;
	}
	
	#changeImg2 {
		font-size: 16px;
		color:#F08200;
	}
</style>